While the economy is a decisive topic in many presidential elections, national security looks increasingly likely to become a top issue in next year’s contest. And if that happens, it could dramatically affect both the direction of the race for the Republican nomination and the party’s prospects in November.

While the economy’s slow recovery hasn’t yet produced solid wage growth or the sort of good, full-time jobs that many had hoped for, President Barack Obama’s job approval numbers on handling the economy have started to climb. Americans are increasingly upbeat about the economy, and Democrats have good reason to believe economic angst won’t be the albatross for them that it was during the past three elections. That’s certainly good news for the eventual Democratic ticket.

But politicians and political strategists planning on making the 2016 election about economic themes and issues may well be preparing to fight the last war.

The success of the Islamic State terror group (also known as ISIL or ISIS), along with beheadings, threats aimed at the West and terrorist attacks in Europe, have damaged the president. Polls show the Islamic State is seen as a threat to the United States, and the president is getting low marks for handling that threat.

Not surprisingly, the news coverage of the Islamic State and terrorism has started to elevate national security issues, particularly for Republicans.

That development, and the likelihood that international crises — whether in the Middle East or involving Vladimir Putin’s Russia — will continue to fester creates challenges for Sen. Rand Paul.

The Kentucky Republican, who apparently is waiting until early April to announce his bid for the GOP nomination, remains an intriguing figure, if only because he isn’t always in step with his own party and understands the GOP must broaden its appeal.

Increasingly, I’ve seen the Kentucky senator as a serious contender for the Republican nomination, since he’ll have both dedicated followers and the financial resources to compete for the long haul. But now, given the increased saliency of foreign policy, I have new doubts about his appeal within the Republican Party.

It is one thing for Paul’s libertarian beliefs to fit uncomfortably within the broad spectrum of Republican positions on immigration, trade or even cultural issues, but it is something very different for his views to run counter to long-time Republican assumptions on national defense and security.

The Kentucky Republican generally has sounded as if the United States should not interfere in other countries’ affairs, though he increasingly tries to finesse security issues and emphasize that he is not an isolationist.

“I’ve said all along that I’m not for 'no interventions,'” Paul said somewhat awkwardly in a September 2014 interview with the Federalist, a conservative Web magazine. “I’m not for saying, ‘We never intervene,' and this is what I’ve spent five years trying to tell people is my policy, I don’t want to be branded as someone who believes in no intervention.”

But that’s not really the issue for most Republican primary voters, who still favor a more muscular approach to foreign policy and defense.

The question for most Republicans isn’t whether the Kentucky Republican rules out all intervention completely, but rather whether his bar for justifying international action is so high and his preferences for cutting all spending, including defense spending, is so strong that a Rand Paul foreign policy would look more like George McGovern’s than Ronald Reagan’s.

Paul, after all, is the same person who in 2011 said , “a more restrained foreign policy is the true conservative foreign policy,” and three years later commented , “the No. 1 threat to our national security is our debt.”

It wouldn’t be at all surprising if his opposition to extending the Patriot Act, support for deep cuts to defense spending and eliminating all foreign aid (including to Israel) and criticism of both Republican and Democratic Middle East policy will lead many Republicans voters to see Paul as too great a foreign policy risk.

If foreign policy and national security become increasingly salient to voters before the 2016 election, those issues will also have a significant impact on the general election.

On one hand, former Secretary of State Hillary Clinton should benefit from that, given her time as the nation’s chief diplomat. She is knowledgeable about international issues and she has dealt with world leaders.

Moreover, while Obama is seen by some as indecisive and even timid when it comes to projecting American military power and standing up to those threatening international stability, Clinton has a very different image. She is widely regarded as tougher than the president.

But as the administration’s former top foreign policy voice, Clinton will have to defend, or at least explain, U.S. policy and answer questions about the nation’s security and influence. No doubt she’ll have to separate herself from Obama on some foreign policy matters, creating some awkward moments and possible problems for her campaign.

Republicans will go directly at Clinton’s foreign policy experience, trying to make her responsible for alleged foreign policy failures and turning her assets into liabilities. Of course, it’s unclear whether that strategy will be successful.

Eventually, the increased salience of national security issues is likely to impact both the mood of voters and their evaluations of the nominees in the GOP nomination fight and in the fall contest.